U.S. patent application number 11/597660 was filed with the patent office on 2007-08-09 for encoder.
This patent application is currently assigned to NOK CORPORATION. Invention is credited to Naoto Kobayashi, Shinji Nagasawa, Yoshiaki Ono, Kenichi Yarimizu.
Application Number | 20070182406 11/597660 |
Document ID | / |
Family ID | 35450980 |
Filed Date | 2007-08-09 |
United States Patent
Application |
20070182406 |
Kind Code |
A1 |
Yarimizu; Kenichi ; et
al. |
August 9, 2007 |
Encoder
Abstract
To easily manufacture an encoder (1), in which N-poles (5) and
S-poles (6) of magnets are arranged alternately in a
circumferential direction and in which an unequal pitch portion (8)
is provided in a part on a circumference, without using a
magnetizing head of a special shape having an unequal pitch
portion, the unequal pitch portion (8) is formed by arranging the
N-poles (5) and the S-poles (6) at an equal pitch all over the
circumference and then providing a part on the circumference with a
shielding member (7) for shielding a magnetism, or the unequal
pitch portion (8) is formed by arranging the N-poles (5) and the
S-poles (6) at an equal pitch all over the circumference and then
providing a part on the circumference with a cut portion.
Inventors: |
Yarimizu; Kenichi;
(Fukushima-shi, JP) ; Nagasawa; Shinji;
(Fukushima-shi, JP) ; Ono; Yoshiaki;
(Fukushima-shi, JP) ; Kobayashi; Naoto;
(Fukushima-shi, JP) |
Correspondence
Address: |
JACOBSON HOLMAN PLLC
400 SEVENTH STREET N.W.
SUITE 600
WASHINGTON
DC
20004
US
|
Assignee: |
NOK CORPORATION
12-15 SHIBADAIMON 1-CHOME MINATO-KU
TOKYO JAPAN
JP
1058585
|
Family ID: |
35450980 |
Appl. No.: |
11/597660 |
Filed: |
April 14, 2005 |
PCT Filed: |
April 14, 2005 |
PCT NO: |
PCT/JP05/07206 |
371 Date: |
November 24, 2006 |
Current U.S.
Class: |
324/207.25 |
Current CPC
Class: |
G01D 5/2457 20130101;
G01D 5/145 20130101 |
Class at
Publication: |
324/207.25 |
International
Class: |
G01B 7/30 20060101
G01B007/30 |
Foreign Application Data
Date |
Code |
Application Number |
May 27, 2004 |
JP |
2004-157027 |
Claims
1. An encoder (1) in which N poles (5) and S poles (6) of magnets
are arranged alternately in a circumferential direction at an equal
pitch and an unequal pitch portion (8) is provided in a part on a
circumference, wherein said unequal pitch portion (8) is formed by
arranging said N poles (5) and said S poles (6) at an equal pitch
all over the circumference and forming a shielding body (7)
shielding a magnetism in a part on the circumference.
2. An encoder (1) in which N poles (5) and S poles (6) of magnets
are arranged alternately in a circumferential direction at an equal
pitch and an unequal pitch portion (8) is provided in a part on a
circumference, wherein said unequal pitch portion (8) is formed by
arranging said N poles (5) and said S poles (6) at an equal pitch
all over the circumference and forming a cut portion (9) in a part
on the circumference.
Description
[0001] This is a nationalization of PCT/JP2005/007206 filed Apr.
14, 2005 and published in Japanese.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an encoder combined with a
magnetic sensor and used for detecting a rotating speed, an angle
of rotation and the like of a rotating part such as a rotating
shaft or the like.
[0004] 2. Description of the Conventional Art
[0005] Conventionally, as shown in FIG. 8, there has been known an
encoder 51 in which N poles 52 and S poles 53 of magnets are
arranged alternately in a circumferential direction at an equal
pitch. Further, for example, in the encoder 51 for an engine in
which it is necessary to specify an angle of rotation of the
rotating shaft, in order to specify a rotational position thereof,
an unequal pitch portion 54 forming a reference point on the
circumference is provided in a part on the circumference.
[0006] However, in conventional, since the encoder 51 is
manufactured by using a magnetizing head having a special shape
provided with the unequal pitch portion in a part on the
circumference of a magnetism applying portion, for forming the
unequal pitch portion 54 in the encoder 51, the magnetizing head is
exclusively used, so that there is a disadvantage that it is
necessary to manufacture the magnetizing head per item of the
encoder 51. The magnetizing head having the special shape provided
with the unequal pitch portion mentioned above has a complicated
shape and is expensive.
[0007] Further, as another conventional art of the present
invention, Japanese Unexamined Patent Publication No. 2003-270258
describes an encoder (a pulsar ring) which is constituted by an
annular support member and at least one band-shaped magnetizing
body attached along a peripheral direction of the annular support
member, and in which mutually facing end magnetic poles of the
magnetizing body are set to be the same pole and a gap is formed in
confronted portion of the magnetizing bodies, whereby a detected
portion for a reference position signal having a small bottom value
existing a peak portion of an output signal is formed at least one
position on a circumference of the ring. However, the conventional
art described in this publication also necessary to use the
magnetizing head having the special shape provided with the unequal
pitch portion.
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
[0008] The present invention is made by taking the points mentioned
above into consideration, and an object of the present invention is
to provide such an encoder that an encoder provided with an unequal
pitch portion can be easily manufactured without using a
magnetizing head or the like having a special shape provided with
the unequal pitch portion.
MEANS FOR SOLVING THE PROBLEM
[0009] In order to achieve the object mentioned above, in
accordance with a first aspect of the present invention, there is
provided an encoder in which N poles and S poles of magnets are
arranged alternately in a circumferential direction at an equal
pitch and an unequal pitch portion is provided in a part on a
circumference, wherein the unequal pitch portion is formed by
arranging the N poles and the S poles at an equal pitch all over
the circumference and forming a shielding body shielding a
magnetism in a part on the circumference.
[0010] Further, in accordance with a second aspect of the present
invention, there is provided an encoder in which N poles and S
poles of magnets are arranged alternately in a circumferential
direction at an equal pitch and an unequal pitch portion is
provided in a part on a circumference, wherein the unequal pitch
portion is formed by arranging the N poles and the S poles at an
equal pitch all over the circumference and forming a cut portion in
a part on the circumference.
[0011] In the encoder in accordance with the first aspect of the
present invention provided with the structure mentioned above,
since the structure is made such that the unequal pitch portion is
formed by arranging the shielding body shielding the magnetism in a
part on the circumference, it is enough that the N poles and the S
poles are arranged in the encoder itself at the equal pitch all
over the circumference. In other words, even if the N poles and the
S poles are arranged at the equal pitch all over the circumference,
the unequal pitch portion can be formed by arranging the shielding
body shielding the magnetism in a part on the circumference.
[0012] Further, in the encoder in accordance with the second aspect
of the present invention provided with the structure mentioned
above, since the structure is made such that the unequal pitch
portion is formed by arranging the cut portion in a part on the
circumference, it is also enough that the N poles and the S poles
are arranged in the encoder itself at the equal pitch all over the
circumference. In other words, even if the N poles and the S poles
are arranged at the equal pitch all over the circumference, the
unequal pitch portion can be formed by arranging the cut portion in
a part on the circumference. In this case, in the manufacturing
process of the encoder in accordance with the second aspect, in a
step of magnetizing the encoder and a step of forming the cut
portion, the former magnetizing step is executed prior to the
latter cutting step, however, the latter cutting step may be
executed in advance.
EFFECT OF THE INVENTION
[0013] The present invention achieves the following effects.
[0014] In the encoder in accordance with the first aspect of the
present invention, since the structure is made such that the
unequal pitch portion is formed by arranging the shielding body
shielding the magnetism in a part on the circumference, it is
enough that the N poles and the S poles are arranged in the encoder
itself at the equal pitch all over the circumference. Accordingly,
it is possible to manufacture the encoder by using a
general-purpose type magnetizing head or the like having no unequal
pitch portion. Further, even in the case of using the
general-purpose type magnetizing head, it is possible to easily
form the unequal pitch portion by arranging the shielding body
shielding the magnetism in a part on the circumference. Further, it
is possible to easily change a magnetic force characteristic of the
encoder by changing a thickness and a width in a circumferential
direction of the shielding body. Further, since it is possible to
visually check the position of the unequal pitch portion, it is
possible to effectively prevent an erroneous assembly.
[0015] Further, in the encoder in accordance with the second aspect
of the present invention, since the structure is made such that the
unequal pitch portion is formed by arranging the cut portion in a
part on the circumference, it is enough that the N poles and the S
poles are arranged in the encoder itself at the equal pitch all
over the circumference. Accordingly, it is possible to manufacture
the encoder by using a general-purpose type magnetizing head or the
like having no unequal pitch portion. Further, even in the case of
using the general-purpose type magnetizing head, it is possible to
easily form the unequal pitch portion by arranging the cut portion
in a part on the circumference. Further, it is possible to easily
change a magnetic force characteristic of the encoder by changing a
depth and a width in a circumferential direction of the cut
portion. Further, since it is possible to visually check the
position of the unequal pitch portion, it is possible to
effectively prevent an erroneous assembly.
BRIEF EXPLANATION OF DRAWINGS
[0016] FIG. 1 is a partly cut perspective view showing a
manufacturing process of an encoder in accordance with a first
embodiment of the present invention;
[0017] FIG. 2 is a partly cut perspective view showing a completed
state of the encoder;
[0018] FIG. 3 is a half cut cross sectional view of the
encoder;
[0019] FIG. 4 is a graph showing a magnetic characteristic of the
encoder;
[0020] FIG. 5 is a partly cut perspective view showing a
manufacturing process of an encoder in accordance with a second
embodiment of the present invention;
[0021] FIG. 6 is a partly cut perspective view showing a completed
state of the encoder;
[0022] FIG. 7 is a half cut cross sectional view of the encoder;
and
[0023] FIG. 8 is a partly cut perspective view of an encoder in
accordance with a conventional art.
DESCRIPTION OF REFERENCE NUMERALS
[0024] 1 encoder [0025] 2 encoder main body [0026] 3 support ring
[0027] 3a flat surface portion [0028] 3b tubular portion [0029] 4
magnetizing portion [0030] 5 N pole [0031] 6 S pole [0032] 7
Shielding body [0033] 7a shielding portion [0034] 7b back surface
portion [0035] 7c connection portion [0036] 8 unequal pitch portion
[0037] 9 cut portion
Best Mode for Carrying Out the Invention
[0038] The present application includes the following
[0039] (1) A magnetization is executed at an equal pitch all over
the surface, and an unequal pitch is achieved by applying the
following process only to a portion where an unequal pitch is
necessary.)
[0040] (a) A magnetic body (a shielding body) is attached only the
unequal pitch portion, and a magnetic force is shielded.
[0041] (b) A rubber (an encoder main body) is removed only from the
unequal pitch portion, and a generation of the magnetic force is
weakened.
[0042] (2) In accordance with the item (a) or (b) mentioned above,
the magnetic head can be constituted by a general-purpose magnetic
head, and can be commonly used.
[0043] (3) A magnetizing method may be constituted by a head type
or an index type.
[0044] (4) In the case of the item (a) mentioned above, since the
magnetic force in the portion can be controlled by a thickness of
the shielding magnetic body, it is possible to freely set within a
gap with respect to the sensor.
[0045] (5) In both of the items (a) and (b) mentioned above, since
the position can be visually checked, it is possible to prevent an
erroneous assembly.
[0046] (6) An encoder in which N poles and S poles of magnets are
arranged alternately in a circumferential direction at an equal
pitch and an unequal pitch portion is provided in a part on a
circumference, wherein the encoder has an encoder main body in
which the N poles and the S poles are arranged at an equal pitch
all over the circumference, and a shielding body attached to a part
on the circumference of the encoder main body and shielding a
magnetism in the position, and a width in a circumferential
direction of the shielding body is formed larger than a width of
one pitch of the N poles or the S poles.
[0047] (7) An encoder in which N poles and S poles of magnets are
arranged alternately in a circumferential direction at an equal
pitch and an unequal pitch portion is provided in a part on a
circumference, wherein the encoder has an encoder main body in
which the N poles and the S poles are arranged at an equal pitch
all over the circumference, and a cut portion provided in a part on
the circumference of the encoder main body and weakening a
magnetism in the position, and a width in a circumferential
direction of the cut portion is formed larger than a width of one
pitch of the N poles or the S poles.
[0048] (8) A forming method of an unequal pitch portion in an
encoder in which N poles and S poles of magnets are arranged
alternately in a circumferential direction at an equal pitch and an
unequal pitch portion is provided in a part on a circumference,
wherein the unequal pitch portion is formed by arranging the N
poles and the S poles in the encoder at an equal pitch all over the
circumference and next attaching a shielding body shielding a
magnetism in a part on the circumference.
[0049] (9) A forming method of an unequal pitch portion in an
encoder in which N poles and S poles of magnets are arranged
alternately in a circumferential direction at an equal pitch and an
unequal pitch portion is provided in a part on a circumference,
wherein the unequal pitch portion is formed by arranging the N
poles and the S poles in the encoder at an equal pitch all over the
circumference and next cutting a part on the circumference so as to
form a cut portion.
[0050] (10) A forming method of an unequal pitch portion in an
encoder in which N poles and S poles of magnets are arranged
alternately in a circumferential direction at an equal pitch and an
unequal pitch portion is provided in a part on a circumference,
wherein the unequal pitch portion is formed by cutting a part on
the circumference of the encoder so as to form a cut portion, and
next arranging the N poles and the S poles at an equal pitch all
over the circumference of the encoder.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0051] Next, a description will be given of embodiments in
accordance with the present invention with reference to the
accompanying drawings.
First Embodiment
[0052] FIGS. 1 to 3 show an encoder 1 in accordance with a first
embodiment of the present invention, in which FIG. 1 is a partly
cut perspective view showing a manufacturing process of the encoder
1, FIG. 2 is a partly cut perspective view showing a completed
state of the encoder 1, and FIG. 3 is a half cut cross sectional
view of the encoder 1, respectively.
[0053] As shown in FIG. 2, the encoder 1 in accordance with the
embodiment is structured such that N poles 5 and S poles 6 of
magnets are arranged alternately at an equal pitch in a
circumferential direction, and an unequal pitch portion 8 is
provided in a part on a circumference. As shown in FIG. 1, the
encoder 1 has an encoder main body 2 in which the N poles 5 and the
S poles 6 are arranged at an equal pitch all over the
circumference, and a shielding body 7 attached to a part on the
circumference of the encoder main body 2 and shielding a magnetism
at this position. Since the shielding body 7 is attached to a part
on the circumference of the encoder main body 2, it is possible to
suppress a radiation of a magnetic signal in this attached
position, whereby the attached position is formed as the unequal
pitch portion 8.
[0054] The encoder main body 2 has a support ring 3, and an annular
magnetizing portion 4 attached to the support ring 3, and the N
poles 5 and the S poles 6 are arranged in the magnetizing portion 4
at an equal pitch all over the circumference. The support ring 3 is
formed in an L-shaped cross section by a magnetic body such as a
metal or the like so as to integrally have an annular flat surface
portion 3a and a tubular portion 3b, and the magnetizing portion 4
is attached to an outer peripheral surface of the tubular portion
3b. The magnetizing portion 4 is formed in a cylindrical shape by a
rubber-like elastic material mixed with a magnetic powder therein,
and is structured such that the N poles 5 and the S poles 6 are
arranged at the equal pitch all over the circumference by a
magnetizing means constituted by a known head system or an index
system or the like.
[0055] The shielding body 7 is formed in a U-shaped cross section
or a J-shaped cross section (the U-shaped cross section in the
drawing) by a magnetic body such as a metal or the like, integrally
has a shielding portion 7a arranged in an outer peripheral surface
side of the magnetizing portion 4, a back surface portion 7b
arranged in an inner peripheral surface side of the tubular portion
3b of the support ring 3, and a connection portion 7c connecting
the shielding portion 7a and the back surface portion 7b, and is
attached to a part on a circumference of the encoder main body 2 by
being pressure inserted to the tubular portion 3b of the support
ring 3 and the magnetizing portion 4 attached to an outer
peripheral surface of the tubular portion from one side in an axial
direction, thereby being structured such as to cover a part on the
circumference of the magnetizing portion 4. Further, a width w1 in
a circumferential direction of the shielding body 7 is formed
larger than a width w2 of one pitch of the N poles 5 and the S
poles 6 (w1>w2). Accordingly, when the shielding body 7 is
attached to the encoder main body 2, the magnetizing portion 4 is
covered over a larger width range than the width w2 of one pitch of
the N poles 5 or the S poles 6. Therefore, the radiation of the
magnetic signal is suppressed in this covered position, whereby the
covered position is formed as the unequal pitch portion 8. In the
drawing, the width w1 in the circumferential direction of the
shielding body 7 is set to a width of two pitches of the N poles 5
or the S poles 6 (w1=w2.times.2).
[0056] The encoder 1 having the structure mentioned above is
attached to a rotating part such as a rotating shaft of the like,
is combined with the magnetic sensor and is used for detecting a
rotating speed, an angle of rotation and the like of the rotating
part, thereby having a feature in a point that the following
operations and effects can be achieved by the above structure.
[0057] Since the encoder 1 having the structure mentioned above is
structured such that the unequal pitch portion 8 is formed by
attaching the shielding body 7 shielding the magnetism to a part on
the circumference of the encoder main body 2 so as to suppress the
radiation of the magnetism at this attached position, it is not
necessary to directly form the unequal pitch portion 8 in the
encoder main body 2 itself, and it is enough to simply arrange the
N poles 5 and the S poles 6 in the encoder main body 2 at the equal
pitch all over the circumference. Accordingly, since it is possible
to manufacture the encoder 1 by using the general-purpose type
magnetizing head or the like having the comparatively simple
structure having no unequal pitch portion, it is possible to
extremely easily manufacture the encoder 1 provided with the
unequal pitch portion 8.
[0058] Further, even if the general-purpose type magnetizing head
or the like is used, it is possible to easily form the unequal
pitch portion 8 by attaching the shielding body 7 shielding the
magnetism to a part on the circumference of the encoder main body
2. A waveform model of a magnetic pulse of the encoder 1 is, for
example, as shown in FIG. 4, and it is possible to easily detect a
position of the origin of the rotating operation on the basis of an
existence of a non-deviation position caused by the unequal pitch
portion 8 shown by reference symbol 8A in the drawing.
[0059] Further, it is possible to easily change a magnetic force
characteristic of the encoder 1 by changing a thickness or the
width w1 in the circumferential direction of the shielding body 7
later attached to the encoder main body 2.
[0060] Further, in accordance with the structure mentioned above,
since it is possible to check the position of the unequal pitch
portion 8 on the basis of an outer appearance of the encoder 1, it
is possible to easily prevent an erroneous assembly.
[0061] In this case, in the embodiment mentioned above, the
structure is made such that the shielding body 7 is formed in the
U-shaped or J-shaped cross section so as to be pressure inserted to
the encoder main body 2 from one side in the axial direction,
however, the mounting structure or the mounting method of the
shielding body 7 to the encoder main body 2 is not limited. The
shielding body 7 may be structured variously as far as the
shielding body 7 is attached to the encoder main body 2 so as to
cover a part of the magnetizing portion 4.
Second Embodiment
[0062] FIGS. 5 to 7 show an encoder 1 in accordance with a second
embodiment of the present invention, in which FIG. 5 is a partly
cut perspective view showing a manufacturing process of the encoder
1, FIG. 6 is a partly cut perspective view showing a completed
state of the encoder 1, and FIG. 7 is a half cut cross sectional
view of the encoder 1, respectively.
[0063] As shown in FIG. 6, the encoder 1 in accordance with the
embodiment is structured such that N poles 5 and S poles 6 of
magnets are arranged alternately at an equal pitch in a
circumferential direction, and an unequal pitch portion 8 is
provided in a part on a circumference. As shown in FIG. 5, the
encoder 1 has an encoder main body 2 in which the N poles 5 and the
S poles 6 are arranged at an equal pitch all over the
circumference, and a cut portion 9 provided by cutting a part on
the circumference of the encoder main body 2 as shown in FIG. 6.
Since the cut portion 9 is provided in a part on the circumference
of the encoder main body 2, it is possible to weaken a radiation of
a magnetic signal in this cut position, whereby the cut position is
formed as the unequal pitch portion 8.
[0064] The encoder main body 2 has a support ring 3, and an annular
magnetizing portion 4 attached to the support ring 3, and the N
poles 5 and the S poles 6 are arranged in the magnetizing portion 4
at an equal pitch all over the circumference. The support ring 3 is
formed in an L-shaped cross section by a magnetic body such as a
metal or the like so as to integrally have an annular flat surface
portion 3a and a tubular portion 3b, and the magnetizing portion 4
is attached to an outer peripheral surface of the tubular portion
3b. The magnetizing portion 4 is formed in a cylindrical shape by a
rubber-like elastic material mixed with a magnetic powder therein,
and is structured such that the N poles 5 and the S poles 6 are
arranged at the equal pitch all over the circumference by a
magnetizing means constituted by a known head system or an index
system or the like.
[0065] The cut portion 9 is formed in a groove shape extending in
an axial direction on an outer peripheral surface of the
magnetizing portion 4, and is formed by magnetizing the magnetizing
portion 4 and thereafter cutting a part on the circumference of the
magnetizing portion 4 in a groove shape. A depth of the groove may
be set to an entire thickness in a diametrical direction of the
magnetizing portion 4, however, may be constituted by a part of the
entire thickness in the diametrical direction of the magnetizing
portion 4 as illustrated, as far as a difference in strength on the
circumference are applied to the generated magnetic signal.
Further, a width w1 in a circumferential direction of the cut
portion 9 is formed larger than a width w2 of one pitch of the N
poles 5 and the S poles 6 (w1>w2). Accordingly, if the cut
portion 9 is provided in the encoder main body 2, the magnetizing
portion 4 is cut over a larger width range than the width w2 of one
pitch of the N poles 5 or the S poles 6. Therefore, the radiation
of the magnetic signal is weakened in this cut position, whereby
the cut position is formed as the unequal pitch portion 8. In the
drawing, the width w1 in the circumferential direction of the cut
portion 9 is set to a width of two pitches of the N poles 5 or the
S poles 6 (w1=w2.times.2).
[0066] The encoder 1 having the structure mentioned above is
attached to a rotating part such as a rotating shaft of the like,
is combined with the magnetic sensor and is used for detecting a
rotating speed, an angle of rotation and the like of the rotating
part, thereby having a feature in a point that the following
operations and effects can be achieved by the above structure.
[0067] Since the encoder 1 having the structure mentioned above is
structured such that the unequal pitch portion 8 is formed by
forming the cut portion 9 obtained by cutting a part of the
magnetizing portion 4 in a part on the circumference of the encoder
main body 2 so as to weaken the radiation of the magnetism at this
cut position, it is not necessary to directly form the unequal
pitch portion 8 in the encoder main body 2 itself, and it is enough
to simply arrange the N poles 5 and the S poles 6 in the encoder
main body 2 at the equal pitch all over the circumference.
Accordingly, since it is possible to manufacture the encoder 1 by
using the general-purpose type magnetizing head or the like having
the comparatively simple structure having no unequal pitch portion,
it is possible to extremely easily manufacture the encoder 1
provided with the unequal pitch portion 8.
[0068] Further, even if the general-purpose type magnetizing head
or the like is used, it is possible to easily form the unequal
pitch portion 8 by forming the cut portion 9 obtained by cutting a
part of the magnetizing portion 4 in a part on the circumference of
the encoder main body 2.
[0069] Further, it is possible to easily change a magnetic force
characteristic of the encoder 1 by changing a depth or the width w1
in the circumferential direction of the cut portion 9 formed by
later attaching to the encoder main body 2.
[0070] Further, in accordance with the structure mentioned above,
since it is possible to check the position of the unequal pitch
portion 8 on the basis of an outer appearance of the encoder 1, it
is possible to easily prevent an erroneous assembly.
[0071] In this case, in the embodiment mentioned above, the process
order is set such that the cut portion 9 is formed after the
magnetizing portion 4 is magnetized, however, the magnetizing
portion 4 may be magnetized after the cut portion 9 is formed.
[0072] Further, commonly in the first and second embodiments, the
magnetizing portion 4 is provided in the outer peripheral surface
of the encoder 1, however, there is a type of encoder in which the
magnetizing portion is provided in an inner peripheral surface of
the encoder or an end surface in an axial direction. The present
invention can be applied to this type of encoder.
* * * * *